1. Field of the Invention
The present invention relates a drainable vehicle wheel having a hub, a rim and a plurality of spokes extending radially from the hub to the rim. More particularly, the present invention relates to a drainable vehicle wheel of the type described in which each of the spokes includes a hollow portion and has one or more fluid-discharge openings formed therein, and to a vehicle incorporating the drainable vehicle wheel.
2. Description of the Background Art
There are known vehicle wheels which are designed to be light in weight and to be stiff against loads of various types. In order to reduce the weight of a vehicle wheel, the vehicle wheel may be manufactured to have one or more hollow structures formed in the one or more spokes thereof. However, since fluid, such as water, may enter the interior of the vehicle with such a hollow structure, the vehicle wheel must be configured to allow the water to be easily drained off.
An example of drainable vehicle wheel (a cast wheel) for a motorcycle, including a hollow portion in which drain holes are formed, is disclosed in Japanese Laid-open Patent Application No. 2005-297688 (FIGS. 1 and 2).
According to this reference, as shown FIG. 1 and FIG. 2 thereof, a cast wheel for a motorcycle includes a hub 1 into which an axle of the vehicle body is inserted; three spokes 3 radially extending from the hub 1; and a rim 2 connected to tip ends of these spokes 3. Each of the spokes 3 has a hollow portion 3c formed therein, which is enclosed with a thin wall portion 3a having a substantially uniform thickness, and a pair of through holes 3b are formed in the thin wall portion 3a at positions close to the rim 2.
If water enters the hollow portion 3c of the vehicle wheel, the water may be drained off through the pair of through holes 3b.
However, since the pair of through holes 3b are formed in the thin wall portion 3a at a predetermined distance away from the rim 2 (and not at tip end portion thereof), water gets collected in the spokes. For example, when the pair of through holes 3b are situated on the lower side (as shown in FIG. 2 of Japanese Laid-open Patent Application No. 2005-297688), water collects up to the level corresponding to the aforementioned predetermined distance in the interior of the spoke portion 3 provided with the through holes 3b. 
Accordingly, due exposure to the water, it is forseeably possible that rust, oxidation or other corrosion may be formed on the inner surface of the spoke portion 3, which may cause reduction in thickness of the wall of each of the spokes 3. As a result, in some areas, the spokes 3 may be decreased in strength.
The present invention has been made to overcome such drawbacks. Accordingly, it is an object of the present invention to provide a drainable vehicle wheel adapted to draw off the water from the hollow portions of the spokes substantially entirely.